Addiction Medicine Practice Questions

Q: What are nitrergic neurons?

First-order neurons releasing nitric oxide.. **Nitrergic neurons** are a specific class of neurons that utilize **Nitric Oxide (NO)** as their primary neurotransmitter. Unlike classical neurotransmitters stored in vesicles, NO is a gaseous molecule synthesized on demand by the enzyme **Neuronal Nitric Oxide Synthase (nNOS)** [1]. **Why Option B is Correct:** In the context of the autonomic and enteric nervous systems, nitrergic neurons are typically **first-order neurons** (primary neurons) that release NO to mediate physiological functions. In the gastrointestinal tract, they are the principal inhibitory neurons of the myenteric plexus, responsible for the relaxation of smooth muscles (e.g., the Lower Esophageal Sphincter and the Sphincter of Oddi) [2]. **Analysis of Incorrect Options:** * **Option A:** While some postganglionic parasympathetic fibers (like those in the corpora cavernosa) release NO, the term "nitrergic neuron" fundamentally refers to the primary/first-order signaling unit in the inhibitory pathways of the enteric nervous system. * **Option C & D:** Substance P and Calcitonin Gene-Related Peptide (CGRP) are neuropeptides associated with **peptidergic neurons**, primarily involved in pain transmission (nociception) and vasodilation, not nitrergic signaling [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Achalasia Cardia:** This condition results from the selective **loss of nitrergic neurons** in the myenteric (Auerbach's) plexus, leading to the failure of the Lower Esophageal Sphincter (LES) to relax. * **Erectile Dysfunction:** NO released from nitrergic nerves in the penis activates guanylyl cyclase, increasing cGMP and causing vasodilation [1]. Sildenafil works by preventing the breakdown of this cGMP. * **Infantile Hypertrophic Pyloric Stenosis:** Also associated with a deficiency of nNOS and nitrergic innervation at the pylorus.

Q: Punctate yellow exudates in the colon, found on endoscopic examination, are indicative of which of the following?

Antibiotic-associated colitis. ### **Explanation** The correct answer is **Antibiotic-associated colitis (Pseudomembranous colitis)**. **1. Why the Correct Answer is Right:** Antibiotic-associated colitis, most commonly caused by **_Clostridioides difficile_ (C. diff)** toxins, is characterized by the formation of **pseudomembranes**. On endoscopic examination (sigmoidoscopy or colonoscopy), these appear as classic **punctate yellow-white exudates** or plaques scattered over the colonic mucosa [1]. These plaques are composed of fibrin, inflammatory cells (neutrophils), and necrotic debris. As the disease progresses, these small punctate spots can coalesce to form larger membranes. **2. Why the Incorrect Options are Wrong:** * **Balantidium coli:** This parasitic infection typically causes **flask-shaped ulcers** (similar to Amoebiasis) rather than yellow exudative plaques. * **Ulcerative colitis:** Endoscopy typically reveals continuous mucosal inflammation starting from the rectum, characterized by **loss of vascular markings, friability, and "lead-pipe" appearance** in chronic cases [1]. It does not present with punctate yellow exudates. * **Gluten-induced enteropathy (Celiac Disease):** This primarily affects the **small intestine** (duodenum/jejunum). Endoscopic findings include scalloping of folds, fissuring, and a mosaic pattern, not colonic exudates. **3. High-Yield Clinical Pearls for NEET-PG:** * **Risk Factor:** Most common after the use of **Clindamycin**, Fluoroquinolones, or 3rd generation Cephalosporins [1]. * **Diagnosis:** The gold standard for diagnosis is the detection of **C. diff toxin A and B** in the stool via PCR or EIA [1]. * **Histology:** Look for the characteristic **"Volcano lesion"** (an eruption of fibrin and PMNs from an ulcerated crypt). * **Treatment:** First-line treatment is oral **Vancomycin** or **Fidaxomicin**. Metronidazole is now reserved for non-severe cases where other options are unavailable.

Q: A person has a history of steatorrhea of long duration. D-xylose testing was performed. A 5-hour urine sample showed <4.5 g excretion after a 25g D-xylose load. What is/are the probable diagnosis?

Celiac disease. The **D-xylose absorption test** is a classic diagnostic tool used to differentiate between **malabsorption** (mucosal disease) and **maldigestion** (pancreatic insufficiency). D-xylose is a monosaccharide that is absorbed in the proximal small intestine by passive diffusion and does not require pancreatic enzymes for digestion [1]. 1. **Why Celiac Disease is Correct:** In Celiac disease, there is diffuse mucosal damage and blunting of the villi in the small intestine. This leads to impaired absorption of D-xylose [1]. A 5-hour urinary excretion of ** 4.5 g** (Normal). 3. **Why Blind Loop Syndrome is Incorrect:** While Small Intestinal Bacterial Overgrowth (SIBO) can sometimes cause a false positive D-xylose test (as bacteria may metabolize the sugar), it is not the primary diagnosis associated with classic mucosal malabsorption in standard NEET-PG scenarios. 4. **Why Ileal Disease is Incorrect:** D-xylose is primarily absorbed in the **duodenum and jejunum**. Disease localized strictly to the terminal ileum (like Crohn’s) typically results in a normal D-xylose test but abnormal Vitamin B12 absorption (Schilling test). **High-Yield Clinical Pearls for NEET-PG:** * **Normal D-xylose test:** Points toward Pancreatic Insufficiency. * **Abnormal D-xylose test:** Points toward Mucosal Disease (Celiac, Tropical Sprue, Whipple’s) [1]. * **False Positives:** Can occur in patients with renal failure, ascites, or delayed gastric emptying. * **Gold Standard for Celiac:** Small bowel biopsy showing villous atrophy and crypt hyperplasia.

Q: A moderate increase in serum aminotransferases with AST/ALT > 3 is suggestive of which of the following?

Alcoholic liver disease. In alcoholic liver disease (ALD), the ratio of **AST to ALT is typically >2:1**, and a ratio **>3:1** is highly suggestive of the diagnosis. ### Why Alcoholic Liver Disease is Correct The biochemical basis for this ratio lies in two factors: 1. **Pyridoxal-5'-phosphate (Vitamin B6) Deficiency:** Chronic alcohol consumption leads to a deficiency of Vitamin B6, which is a required co-factor for ALT synthesis. Consequently, ALT levels remain relatively low even during liver injury. 2. **Mitochondrial Damage:** Alcohol is a mitochondrial toxin [1]. AST exists in both cytosolic and mitochondrial forms; alcohol-induced damage causes the preferential release of mitochondrial AST [1]. In ALD, the absolute values of transaminases are usually only **moderately elevated** (typically 1000 IU/L) with an **AST/ALT ratio 5000 IU/L) and LDH. * **Drug Hepatotoxicity:** Most drugs (except for specific toxins like acetaminophen in the late stage) typically present with an **AST/ALT ratio 2, think Alcohol. If ALT > AST, think Viral or Fatty Liver (NAFLD).

Q: The pathogenesis of hypochromic anemia in lead poisoning is due to which of the following mechanisms?

Inhibition of enzymes involved in heme biosynthesis. Lead poisoning (Plumbism) causes a microcytic hypochromic anemia primarily by interfering with the enzymatic pathway of heme synthesis. **1. Why Option A is Correct:** Lead inhibits two critical enzymes in the heme biosynthetic pathway: * **Delta-aminolevulinic acid dehydratase (ALAD):** Lead inhibits this enzyme, preventing the conversion of ALA to porphobilinogen [1]. This leads to an accumulation of ALA in the blood and urine. * **Ferrochelatase:** This enzyme is responsible for incorporating iron into the protoporphyrin ring to form heme [3]. Lead inhibits this step, resulting in an accumulation of **erythrocyte protoporphyrin**. The lack of heme production results in decreased hemoglobin synthesis, leading to the characteristic **hypochromic anemia**. **2. Why Other Options are Incorrect:** * **Option B & D:** Lead does not significantly interfere with iron transport (transferrin) or storage (ferritin/hemosiderin). The iron is available, but the cell cannot utilize it to make heme due to enzyme inhibition. * **Option C:** While lead does bind to red cell membranes and inhibits the enzyme **5'-nucleotidase** (leading to **basophilic stippling** due to RNA degradation failure) [2], this mechanism contributes to hemolysis rather than the primary defect in hemoglobin synthesis (hypochromia). **High-Yield Clinical Pearls for NEET-PG:** * **Basophilic Stippling:** Coarse blue granules in RBCs (retained RNA) is a classic peripheral smear finding [2]. * **Burton’s Line:** Bluish-purple line on the gingival margin [2]. * **Radiology:** "Lead lines" (increased density) at the metaphyses of long bones in children [2]. * **Treatment:** Chelation therapy with **Succimer** (oral, first-line in kids), **Ca-EDTA**, or **Dimercaprol (BAL)** [4].

Question 1

What are nitrergic neurons?

Accepted Answer

First-order neurons releasing nitric oxide.

Answer

Postganglionic neurons releasing nitric oxide.

Answer

Postganglionic neurons releasing substance P.

Answer

First-order neurons releasing calcitonin gene-related peptide.

Question 2

Punctate yellow exudates in the colon, found on endoscopic examination, are indicative of which of the following?

Accepted Answer

Antibiotic-associated colitis

Answer

Balantidium coli

Answer

Ulcerative colitis

Answer

Gluten-induced enteropathy

Question 3

A person has a history of steatorrhea of long duration. D-xylose testing was performed. A 5-hour urine sample showed <4.5 g excretion after a 25g D-xylose load. What is/are the probable diagnosis?

Accepted Answer

Celiac disease

Answer

Pancreatitis

Answer

Blind loop syndrome

Answer

Heal disease

Question 4

A moderate increase in serum aminotransferases with AST/ALT > 3 is suggestive of which of the following?

Accepted Answer

Alcoholic liver disease

Answer

Acute viral hepatitis

Answer

Prolonged hypotension

Answer

Drug hepatotoxicity

Question 5

The pathogenesis of hypochromic anemia in lead poisoning is due to which of the following mechanisms?

Accepted Answer

Inhibition of enzymes involved in heme biosynthesis

Answer

Binding of lead to transferrin, inhibiting the transport of iron

Answer

Binding of lead to the cell membrane of erythroid precursors

Answer

Binding of lead to ferritin, inhibiting their breakdown into hemosiderin

Addiction Medicine — MCQs

Addiction Medicine — MCQs

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